Collapsible energy absorbing vehicular steering columns for application on vehicle steering systems have been well known and in popular use for a number of years. Some collapsible steering systems have frangible parts or have parts capable of relative movement under the action of impact forces. These systems generally comprise a significant number of parts and are relatively bulky.
One such collapsible steering shaft assembly is shown in U.S. Pat. No. 4,183,258 to Stephan. This patent discloses a collapsible shaft assembly comprising an outer sleeve forming a universal coupling with a coaxial inner sleeve disposed within the outer sleeve. A coaxial elastomeric sleeve is placed in radial compression within the inner and outer sleeves. A shaft is rotatably coupled to and axially slidable within the inner sleeve. A shearable lock is provided to hold the shaft axially relative to the inner sleeve up to a given, minimum axial load. When the lock shears in the presence of sufficient axial force, limited collapse is allowed.
U.S. Pat. No. 5,024,118 to Khalifa discloses a steering column guide structure for a collapsible steering column assembly. Triangular guide members adjacent to and above the upper portion of the steering column prevent upward movement of the upper portion of the steering column upon collapse of the column. A guide collar is provided around the lower portion of the steering column to axially guide the lower portion upon collapse. Energy is absorbed by deformation of the lower bracket 26. Frangible tabs are provided to allow the retainer 44 to move out of the way in order to allow energy absorption to occur at the lower support bracket during collapse. This design is structurally cumbersome because it is mounted to the vehicle at both the upper and lower support brackets, and it allows only limited column collapse.
It is desirable to provide a simple steering column assembly design which includes tilting and telescoping movement of the steering column shaft and includes a single releasable mounting point which allows further collapse of the intermediate steering column shaft into the engine compartment when the upper portion of the assembly has fully collapsed upon presentation of a sufficient axial load. Further, the overall design must be sufficiently universal to fit numerous vehicular applications.